I was in a similar position few months ago, getting bored doing the same thing again and again. I could have changed jobs for a better pay and profile but it would not have been a significant improvement in work quality. Also the job was intense so I would end up thinking about the startup all the time with no time left for personal projects. I have decided to take a break of couple of years to learn new stuff I have already made a list of, experiment with some personal projects I always wanted to create and figure out what I would like to do later. Just ensure that you have a fair bit of runway so that if any of your projects get serious you can pursue it to end.